Ink



Patented May 8, 1945 INK Bernard L. Kline, Manhasset, N. Y., assignor toThe Western Union Telegraph Company, New York, N. Y., a corporation ofNew York No Drawing. Application August 1, 1940, Serial No. 349,239

.7Claims.

This invention relates to inks, and more particularly to inks forsaturating the inking members of type wheel printers, such as are usedin printing telegraph apparatus, although the inks of the invention maybe used effectively for other purposes, for instance, for impregnatinginking ribbons, stamp pads, and like members. The novel methods ofprinting and the novel inks employed in obtaining the new resultsdisclosed herein include subject matter divided out of copendingapplication, Serial No. 642,323, filed November 11, 1932.

In printing telegraph systems, and other cases where printed charactersare obtained by trans- [er of ink from an inking member to a printingmember, as in a, type wheel printer, or directly to the printingsurface, as in the ordinary typewriter, a number of different mediumsare used to receive the printed record, each of which presents adifferent kind of printing surface.

The present invention in one of its aspects aims to provide inks whichare suitable, not only for printing on a wide variety Of printingsurfaces, but also inks which are specially adapted for transfer tosurfaces which do not readily receive printed impressions. The principalones of the mediums used to receive printed impressions in the order oftheir increasing interfacial tension with ordinary inks are (l) cloth;(2) ordinary untreated papers which have comparatively rough and poroussurfaces; (3) parchment; (4) transparent pressed, regenerated orreconstituted cellulose in the form of tape or sheets; (5) a papercalendered under high temperature to render it transparent-this paperhas a comparatively rough but non-porous surface; (6) transparentcellulose esters molded or formed into tape or sheets, the surfaces ofwhich are microscopically smooth but which are resistant to wetting; and('7) oiled or waxed papers which are extremely resistant to wetting. Theinks of this invention can be suited to the printing surface so thatinterfacial tension between the surface and the ink will give printedimpressions free from mottling caused by gathering of the globules, oron the other hand, without excessive spreading due to too low aninterfacial tension between the ink and the printing surface.

Since the surface characteristics of the materials named above asexamples of common mediums used to receive printed records are widelydivergent, it has been necessary heretofore to formulate a special inkfor each surface.

Oneof the objects of the present invention is to produce inks which maybe used satisfactorily for printing upon 'a large number of dlflerentkinds of surfaces.

Another and related object of the invention is to produce inks suited.to the surface characteristics of special printing materials.

Still another object is to produce an improved ink for recording upontapes which are resistant to wetting, such as cellulose or celluloseester A still further object is to produce an ink which is inexpensive,simple to manufacture, and which will not deteriorate with age.

The novel inks to be disclosed herein employ alcohol type solvents,containing hydroxyl radicals but containing no ester groups, as thevehicle carrying the coloring matter. This chemical class of materialsis specially useful in compounding inks because it has excellent solventproperties for methyl violet and also because it possesses specialoptical properties. Inks compounded with these solvents appear to passmost of the wave length bands of visible light permitting the coloringmatter to fulfill its function since the vehicle transmits both red andblue light. This is especially useful where printing is done ontransparent materials which are to be used in stock quotation projectorsand the like.

Therefore, still another object of the invention is to produce an inkcapable 'Of affording printed characters having more intense coloringthan inks available prior to this invention.

Still another object is to provide an ink for type wheel printers usingimpregnated ink dispensing members, with which the dispensing membersmay be reimpregnated as often as desired, which will not dry on thedispensing member and which will not affect metal or rubber parts of theprinter.

A still further object is to produce an ink which does not readilyabsorb moisture.

Other objects and advantages of the invention disclosed herein willappear in the following detailed description.

The inks heretofore developed for printing upon cellulose acetate tapedepend upon the use of a solvent for the tape in the ink which enablesthe ink to wet the tape and therefore produce an impression thereon.This ink is not suitable for other types of tape, however, such ascellulose or paper, since the solvent has no action thereon. For suchsurfaces, variations in the viscosity of the ink to obtain a medium oftackiness has been depended upon. This necessitates the provision of anink having a different degree of Viscosity for each type of surface tobe printed upon and such inks have not proven particularly satisfactoryfor printins upon materials which in general have a high interfacialtension, such as the cellulose or cellulose acetate tapes.

The ink mostly used in printing for ticker type wheels in the pastconsists of a mixture of alcohol and glycerine containing when newapproximately 12% of methyl violet in solution. Methyl violet is a.powerful aniline dye having the property of maintaining its shade evenwhen diluted. However, only about 12% of the dye will go in the solutionand since alcohol is very volatile even this percentage of dye does notstay long in the solution. Ink rollers impregnated with this ink must beused soon after preparation and are of relatively short life due to theevaporation of the alcohol and the consequent precipitation of some ofthe dye in the felt rollers. Such rollers cannot be reimpregnated sincethe precipitated dye renders them unfit for further use and will not bereadily reabsorbed by any subsequent treatment.

Moreover, the glycerine used in the ink absorbs water from the air,changing the consistency of the ink and rendering the printing erraticand dependent upon humidity conditions. This ink is not very suitablefor tapes of the cellulose of cellulose acetate type since the glycerinedoes not properly wet the surfaces thereof and consequently the printingis light and not satisfactory for projection purposes.

In accordance with the present invention a new principle of formulatinginks is employed whereby inks are produced which print or write on allclasses of printing mediums substantially.

equally well. In place of depending upon the viscosity of the ink orupon its dissolving efiect on the receiving medium, I control thewetting of the tape by interfacial tension between the printing surfaceand the ink through regulation of the surface tension of the ink. I havefound that if the surface tension of the ink is suited to the printingsurface, the ink will wet all types of tape without dissolving them andwill spread sumciently to form uniform characters without mottling orspreading. 1

In carrying out the invention disclosed herein it is preferred to employmethyl violet as the primary coloring agent, due to the strong contrastailorded thereby, and to its relative cheapness, although it is to beunderstood that any other suitable aniline or other kind of dye orcoloring matter may be employed for the production of inks of othercolors.

In order to render the ink resistant to evaporation and thereby toenable impregnated rollers or ribbons to be stored for long periods, asolvent for the dye is preferred which has a high boiling point,preferably over 350 F.

The solvents which have been found most satisfactory as vehicles areorganic solvents of the alcohol type and more particularly lycols andtheir corresponding ethers. These solvents have surface tensions rangingfrom about 15 dynes per centimeter to about 50 dynes per centimeter andmany combinations or these solvents are possible to produce a suitablesolvent having a surface tension between 25 and 30 dynes per centimeter.These materials in addition to having a high boiling point readilydissolve the aniline dyes, and many of these solvents have an extremelylow surface tension, such as carbitol, butyl carbltol and amyleneglycol. In order to make a satisfactory ink these are mixed with othershaving higher surface tensions, such a; diethylene glycol andtriethylene glycol. The surface tension of these latter compounds ishigh compared to that of the former group and by properly preparing themixture, the surface tension most suitable for printing, under manyconditions, may be obtained. After numerous mixtures were tried, it wasfound that best results for printing upon the mediums disclosed hereinwere obtained with a combination of butyl carbitol containing aproportion of both diethylene glycol and triethylene glycol. The wettingability of the solvent is regulated primarily by dilution withdiethylene glycol and the viscosity somewhat altered by the addition ofthe triethylene glycol.

Due to the high solubility of these materials for methyl violet, the dyecontent may be increased over that used in prior inks up to about 24%,thereby rendering the characters printed with the ink heavier and darkeror more opaque. This i of particular advantage in connection withprinting upon transparent mediums for projection upon a screen inenlarged characters.

Many of the organic solvents not embraced in the class of alcoholmaterials having a high boiling point and being free of ester groupsappear to hav the property of filtering light so as to reduce passage ofreds in the neighborhood of 650 to 750 millimicrons. This appears to beso since methyl violet when carried by these non-alcohol type vehiclesloses its red cast and appears bluish. The obvious effect of thisapparent optical property of many of the solvents is to cause loss ofopacity or contrast of the printed characters.

The high boiling solvents of the alcohol type apparently do not exert arefraction or absorption eiiect on the longer wave lengths of visiblelight inasmuch as inks compounded with methyl violet have a reddish castand characters printed on a transparent material and projected on ascreen are dark and contrasting to the human eye.

Tests made on these printed characters using a standard photocellproduce substantial response in the photocell, indicating thatsubstantial red is refracted into the photocell since the photocell ismost responsive in this red range. Printed characters lacking thisreddish cast, on the other hand, do not stimulate the photocell,indicating a deficiency in the red range. These observations taken witha photocell corroborate the visual effect.

Examples of satisfactory solvents of the class described are propyleneglycol, dipropylene glycol, butylene glycol, amylene glycol, diethyleneglycol, triethylene glycol, trimethylene g ycol, tetramethylene glycol,tetraethylene glycol, carbitol (the monoethyl ether of diethyleneglycol), and butyl carbitol (the monobutyl ether of diethylene glycol).Certain of these, such as carbitol (surface tension 28 dynes), butylcarbitol (24 dynes), and amylene glycol (17 dynes) may be used alongwith others having a higher surface tension, such as diethylene glycol(38 dynes) and triethylene glycol (34 dynes). Any of these materials maybe used alone or in combination,

depending on the class of surface to be printed upon.

In efiect, this means that when the requirement is to print on oiled orwaxed papers, carbitol, butyl carbitol, or amylene glycol are usedalone. In printing on cellulose tape or surfaces of cellulose esters oron highly calendered papers, such as glassine, mixtures of thesematerials are made with other solvents of higher surface tension toincrease the final surface tension to between and dynes per centimeter.

When ordinary paper is required to be printed upon, the use of lowsurface tension solvents will produce spreading or feathering of thecharacters and for this reason solvents or mixtures having surfacetensions between 25 and dynes will produce best results. For the mosthighly absorbent surfaces, such as cloth or low sized paper, surfacetensions even above dynes are most suitable.

Due to the high solubility of these materials for methyl violet, the dyecontent may be increased over that used in prior inks, up to about 24%,thereby rendering the characters printed with the ink heavier and darkeror more opaque. This is of particular advantage in connection withprinting upon transparent mediums for projection upon a screen inenlarged characters.

The formula found most satisfactory for purple ink is as follows:

. Per cent Butyl carbitol 34.3 Diethylene glycol 26.4 Triethylene glycol15.3 Methyl violet 24.0

If a darker ink is desired, it may be obtained by mixing another anilinedye with the methyl violet. This has the effect of rendering the purplecolor of this latter dye dirty and hence darker in color. Chrysoidine Y,an orangeyellow dye, is particularly effective for this purpose, servingwhen added in the proper proportion, of toning the ink to a dark ordirty purple which has the property of seeming almost black and which,unlike ordinary blacks. does not gray or give the impression of fadingout when the type wheel is lightly inked. This effect may be enhanced byadding a small proportion of malachite green to the other two dyes.

Obviously, any other mixture of dyes may be used either to produce anear black ink or to obtain any desired color effects. The preferredformula when using the methyl violet and chrysoidine Y color mixture isas follows:

Per cent Butyl carbitol 39.4 Diethylene glycol 25.7 Triethylene glycol10.9 Methyl violet 13.7 Chrysoidine Y 6.5 Malachite green 3.8

As stated, this ink, due to its low surface tension. wets not only theplain papers and those calendered under high temperature and pressure torender them transparent, but also the cellulose and cellulose acetatetapes, thereby enabling printing to be effected equally well on allsurfaces and permitting the inking rollers for all machines to beimpregnated uniformly and therefore requiring but a single stock.

When printing upon a porous medium, such as ordinary paper, the ink ofthe formula just given is substantially non-smudging since, due to itslow surface tension, it penetrates into the paper very rapidly. On theaforementioned calendered papers as well as on the cellulose tapes, bothof which have relatively rough surfaces, the ink flows freely into thedepressions of the paper, beneath the type, forming a continuousimpression as distinguished from the mottled effect produced by the moreviscous inks, due to the fact that they rest mainly on the high spots ofthe paper or tape,

The cellulose acetate tape presents one of the most difllcult surfacesto print upon since this material is very resistant to wetting. However,due to the low surface tension of the ink there is a low interfacialtension produced between the ink and the tape, causing the ink to flowevenly and to wet all portions of the tape in contact with the typewheel. The characters produced on this material are solid and clean cut,and due to the high dye content of the ink they are dark and opaque,rendering the printing particularly suitable for projection upon ascreen.

The untreated paper, of course, wets quite easily, whereas theresistance of wetting of the aforementioned calendered paper or thecellulose tape is intermediate that of the untreated paper and thecellulose acetate tape. The surface tension of the ink should beregulated so that it just wets the rough and porous surface of theuntreated paper satisfactorily, having sufficient viscosity, however, soas not to spread unduly on the cellulose acetate. The surface tension ofthe ink, for satisfactorily wetting of all the surfaces described,should range from about 25 to 30 dynes per centimeter at roomtemperature, the most favorable action of all mediums being obtainedwith a surface tension f approximately 27 dynes per centimeter.

Butyl carbitol has a surface tension of about 24 dynes per centimeter.The diethylene glycolv having a surface tension of about 38 dynes percentimeter, is added in proper proportion to increase the surfacetension to the desired value. Triethylene glycol, having a surfacetension of about 34 dynes per centimeter, may also be used to controlthe surface tension of the ink solvent. The viscosity of this lattersolvent is somewhat greater than that of diethylene glycol, and I havefound that the best results are obtained by m using a mixture ofdiethylene glycol and triethylene glycol, thereby regulating both thesurface tension and the viscosity of the ink.

As a matter of comparison the usual alcohol glycerine vehicle usedheretofore for inks for type wheel printers, when new has a surfacetension of around 40 dynes per centimeter. The alcohol evaporates veryrapidly, however, so that the proportion of alcohol and glycerinechanges, and since glycerine has a relatively high surface tension ofaround 63.5 dynes per centimeter, the surface tension of the inkgradually increases during use and is normally much higher than 40. Thisink does not depend upon surface tension for its printing quality butupon its viscosity, and it is not suitable except for printing uponplain paper, or similar surfaces.

It is to be understood that the range of surface tension specified isfor an ink having the property of wetting or printing upon a largenumber of surfaces having widely differing characteristics, that is. fora universal ink. For specific surfaces surface tension outside of therange specified may be preferred, and therefore I do not desire to belimited to the specific range given, the same being specified merely asa guide to assist in the practice of the invention. When the properconditions of surface tension are met as specified above, the ink willproduce good impressions on all surfaces of an intermediate nature, andit may be used both for impregnating the usual felt inking rollers orribbons for type bar machines, and it may be used for writing with penupon such surfaces. The ink is sufllciently fluid so that it may be usedin fountain pens, or automatic syphon recording devices.

The method of compounding the ink is comparatively simple, since itrequires no grinding or extensive mechanical mixing of the ingredients.The solvents are first mixed in the proper proportions by weight in aflat bottomed metal container having a capacity about double the amountof ink being made. Preferably the depth of the container should be aboutthree-quarters of its diameter or the length of one side. The solventsare then heated by applying the heat uniformly over the bottom of thevessel, to a temperature of about 140 to 150 E, which temperature ismaintained through. the process. The required amount of dye (which is inpowder form) is added slowly to the heated solvents with constantstirringby means of a wooden paddle or wooden rod until all the dye hasbeen added and all of the lumps or settlings have been dissolved. Theink is then complete and may be used for imregnating the rollers or itmay be cooled and stored for later use.

While heating of the ink during manufacture is preferred, since itenables solution to take place more rapidly, equally good results may beproduced by stirring only, at room temperature.

The rollers to be impregnated are placed on their sides in a. singlelayer in a wire basket of a size to fit the ink container, the basketbeing lowered into the ink while the latter is heated to about 140 to150 F., until the rollers are not more than one-half submerged. Completesub merging of the rollers will trap the air in the felt and preventcomplete impregnation. The ink is allowed to soak up through the feltand wooden bobbins on which the felt is mounted, until no cleanunimpregnated areas are left. This will require from two to six minuteswith rollers of ordinary size, depending upon the temperature.

The rollers are then quickly submerged for an instant and then removedfrom the ink and permitted to drain after which they are allowed tocool. They are then ready for use.

Since the solvents used in the ink have a high boiling point, they donot evaporate from the rollers and therefore the concentration thereofdoes not change, nor does the dye precipitate out of the solution.However, the, ink does not absorb as much water from the air as doglycerine inks and consequently its consistency remains substantiallyconstant in all kinds of weather. The rollers therefore may be storedfor long periods of time without deteriorating and as fast as the ink isused up therefrom they may be impregnated over and over until they arerendered unfit for use due to wear.

The ink after it has been stored may be prepared for use again, bymerely warming to 140 to 150 F. with constant stirring.

- While I have specified certain solvents, other compounds of thechemical class disclosed which dissolve a sufficient quantity of the dyeand have the requisite high boiling point, low surface tension, opticalproperties, and non-corrosive action on the printer parts, may beemployed. Therefore, I do not desire to be limited to the specificformulas given herein but contemplate the use of all equivalentingredients therein as coming with. in the scope of the appended claims.

What is claimed is:

l. A subtantially non-volatile ink comprising a dye dissolved in amixture of two or more organic alcohol type solvents of the classconsisting of glycols and glycol ethers each having a boiling point ofat least 350 F. said solvents respectively having different surfacetension characteristics and different boiling points; and theproportions of the solvents being such that said mixture has a surfacetension of theorder of between 25 and 3g dynes per centimeter and aboiling point above 3 0 F.

2. A substantially non-volatile ink comprising a dye dissolved in amixture of two or more organic alcohol type solvents of the classconsisting of ethylene glycols and their ethers each having a boilingpoint of at least 350 F., said solvents respectively having differentsurface tension characteristics and different boiling points, and theproportions of the solvents being such that said mixture has a surfacetension of the order of between 25 and 30 dynes per centimeter and aboiling point above 350 F.

3. A substantially non-volatile ink comprising a dye dissolved in amixture of butyl carbitol,-diethylene glycol and triethylene glycol, theproportions of said solvents being such that said mixture has a surfacetension of the order of between 25 and 30 dynes per centimeter.

4. A substantially non-volatile fiuidink comprising methyl violetdissolved in a mixture of butyl carbitol and a glycol, the proportionsof said solvents being such that the mixture has a surface tension ofthe order of between 25 dynes and-i0 dynes per centimeter. v

5. An ink comprising a. dye dissolved in a mixture of butyl carbitol,diethylene glycol,and triethylene glycol, the proportions of saidsolvents being such that the mixture has a surface tension of the orderof between 25' dynes and 40 dynes per centimeter. I

6. An ink having the following formula:

Per cent Butyl carbitol "Approximately" 34.3 Diethylene glycol do 26.4Triethylene glycol do 15.3 Soluble dye do 24.0

7. A printing ink comprising by weight from 32.5% to 34.5% approximatelyof butyl carbitol, diethylene glycol 22.5% to triethylene glycol 9.5% to14.5%, and an aniline dye, from 10% to 33.5%.

BERNARD L. KLINE.

